1. Field of the Invention
The present invention relates to storage systems, and more particularly, to data replication among a plurality of storage systems and resuming data replication processing when failures occur in the storage systems.
2. Related Background Art
In recent years, in order to provide continuous service to clients at all times, technologies concerning data replication among storage systems have become important to make it possible for a data processing system to provide services even when a failure occurs in a first storage system. There have been technologies for replicating information stored in the first storage system on second and third storage systems.
For example, according to one of the known technologies, a first storage system stores data in a first storage system, and transfers data stored in the first storage system to a second storage system, as well as to a third storage system. A computer and the first storage system are connected by a communications link, the first storage system and the second storage system are connected by a communications link, and the first storage system and the third storage system are also connected by a communications link. The first storage system has a first logical volume that is the subject of replication. The second storage system has a second logical volume that is a replication of the first logical volume. The third storage system has a third logical volume that is a replication of the first logical volume. The first storage system, when updating the first logical volume, performs a data replication processing on the second logical volume, and stores in management information a difference between the first logical volume data and the third logical volume data for every data size of a predetermined size. Subsequently, the first storage system uses the management information to perform a data replication processing on the third logical volume.
The conventional technology described manages the difference in data between the first logical volume and the third logical volume for every data size of a predetermined size. The management information that manages such differences entails a problem of growing larger in proportion to the amount of data that is the subject of replication. Furthermore, due to the fact that the third logical volume is updated based on the management information and in an order unrelated to the order of data update, data integrity cannot be maintained in the third logical volume.